Among the compounds which fall under the general formula described above, some of .omega.-(p-substituted phenoxy)-2,2-dimethylalkanoic acid esters are described in Published Unexamined Japanese Patent Application 6667-85 or EP pat. appln. pub. No. 130,077 together with physical data thereof and are known. In the patent application supra, mention is made of utility of these compounds as medicines that they possess excellent activity of inhibiting platelet agglutination.